blabla1337 / ble_ctf

A Bluetooth low energy capture the flag

BLE Capture the Flag

The purpose of BLE CTF is to teach the core concepts of Bluetooth Low Energy client and server interactions. While it has also been built to be fun, it was built with the intent to teach and reinforce core concepts that are needed to plunge into the world of Bluetooth hacking. After completing this CTF, you should have everything you need to start fiddling with any BLE GATT device you can find.

Setting Up the CTF

In order to set up the CTF you will need the following:

1. The code in this repository to build the CTF GATT server
2. An esp32 microcontroller (I sell overpriced pre-flashed ones here)
3. A Linux box (OSX/Win + Linux VM works) with a bluetooth controller or a bluetooth usb dongle (I ❤️ UD100s)
4. Bluetooth tools such as Bluez tools (hcitool, gatttool, etc) or bleah

To get setup, read this documentation

Flags

How to Submit Flags

Before you can submit flags, you have to discover the Bluetooth MAC address of your device. Here are a couple example commands to help you find your device:

Discover MAC using hcitool:
sudo hcitool blescan

Discover MAC using bleah:
sudo bleah

Now that you have found your device’s MAC address, you can now communicate with it. Before we get started with flags, let’s check out how we can see our current score. In order to see where you are in the CTF, you can read from handle 42 on the device to see how many flags you have. The following are example commands of how to view your current score. Make sure you replace the MAC address in the example commands with the MAC address of your device.

Show score with gatttool:
gatttool -b de:ad:be:ef:be:f1 --char-read -a 0x002a|awk -F':' '{print $2}'|tr -d ' '|xxd -r -p;printf '\n'

Show score with bleah:
sudo bleah -b "30:ae:a4:20:79:da" -e

Ok, ok, ok, on to the flags! All flags are md5 sums truncated to 20 characters to avoid MTU limits by some hardware. They can be submitted to the gatt server on handle 44. The following are examples of how to submit a flag. Make sure you replace the MAC address in the example commands with the MAC address of your device:

Submit using gatttool:
gatttool -b de:ad:be:ef:be:f1 --char-write-req -a 0x002c -n $(echo -n "some flag value"|xxd -ps)

Submit using bleah:
sudo bleah -b "30:ae:a4:20:79:da" -n 0x002c -d "some flag value"

Flag Hints

Flag	Description	Hint
Flag 1	This flag is a gift and can only be obtained from reading the hint!	Read Me!
Flag 0x002e	Learn how to read handles	More
Flag 0x0030	Read handle puzzle fun	More
Flag 0x0016	Learn about discoverable device attributes	More
Flag 0x0032	Learn about reading and writing to handles	More
Flag 0x0034	Learn about reading and writing ascii to handles	More
Flag 0x0036	Learn about reading and writing hex to handles	More
Flag 0x0038	Learn about reading and writing to handles differently	More
Flag 0x003c	Learn about write fuzzing	More
Flag 0x003e	Learn about read and write speeds	More
Flag 0x0040	Learn about single response notifications	More
Flag 0x0042	Learn about single response indicate	More
Flag 0x0046	Learn about multi response notifications	More
Flag 0x0048	Learn about multi response indicate	More
Flag 0x004c	Learn about BT client device attributes	More
Flag 0x004e	Learn about message sizes MTU	More
Flag 0x0050	Learn about write responses	More
Flag 0x0052	Hidden notify property	More
Flag 0x0054	Use multiple handle properties	More
Flag 0x0056	OSINT the author!	More